* [PATCH] dm ioctl: Access user-land memory through safe functions.
@ 2015-12-01 18:11 Scotty
2015-12-08 18:26 ` Scotty Bauer
0 siblings, 1 reply; 7+ messages in thread
From: Scotty @ 2015-12-01 18:11 UTC (permalink / raw)
To: agk, snitzer; +Cc: linux-kernel, dm-devel
[-- Attachment #1: Type: text/plain, Size: 0 bytes --]
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-dm-ioctl-Access-user-land-memory-through-safe-functi.patch --]
[-- Type: text/x-patch; name="0001-dm-ioctl-Access-user-land-memory-through-safe-functi.patch", Size: 1533 bytes --]
From b26adf880eba03ac6f2b1dd87426bb96fd2a0282 Mon Sep 17 00:00:00 2001
From: Scotty Bauer <sbauer@eng.utah.edu>
Date: Tue, 1 Dec 2015 10:52:46 -0700
Subject: [PATCH] dm ioctl: Access user-land memory through safe functions.
This patch fixes a user-land dereference. Now we use
the safe copy_from_user to access the memory.
Signed-off-by: Scotty Bauer <sbauer@eng.utah.edu>
---
drivers/md/dm-ioctl.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 80a4395..39a9d1a 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1642,9 +1642,13 @@ static ioctl_fn lookup_ioctl(unsigned int cmd, int *ioctl_flags)
static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
{
uint32_t version[3];
+ uint32_t __user *version_ptr;
int r = 0;
- if (copy_from_user(version, user->version, sizeof(version)))
+ if (copy_from_user(&version_ptr, &user->version, sizeof(version_ptr)))
+ return -EFAULT;
+
+ if (copy_from_user(version, version_ptr, sizeof(version)))
return -EFAULT;
if ((DM_VERSION_MAJOR != version[0]) ||
@@ -1663,7 +1667,7 @@ static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
version[0] = DM_VERSION_MAJOR;
version[1] = DM_VERSION_MINOR;
version[2] = DM_VERSION_PATCHLEVEL;
- if (copy_to_user(user->version, version, sizeof(version)))
+ if (copy_to_user(version_ptr, version, sizeof(version)))
return -EFAULT;
return r;
--
1.9.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] dm ioctl: Access user-land memory through safe functions.
2015-12-01 18:11 [PATCH] dm ioctl: Access user-land memory through safe functions Scotty
@ 2015-12-08 18:26 ` Scotty Bauer
2016-01-05 20:16 ` Mike Snitzer
0 siblings, 1 reply; 7+ messages in thread
From: Scotty Bauer @ 2015-12-08 18:26 UTC (permalink / raw)
To: agk, snitzer; +Cc: linux-kernel, dm-devel
On 12/01/2015 11:11 AM, Scotty wrote:
>
> 0001-dm-ioctl-Access-user-land-memory-through-safe-functi.patch
>
>
> From b26adf880eba03ac6f2b1dd87426bb96fd2a0282 Mon Sep 17 00:00:00 2001
> From: Scotty Bauer <sbauer@eng.utah.edu>
> Date: Tue, 1 Dec 2015 10:52:46 -0700
> Subject: [PATCH] dm ioctl: Access user-land memory through safe functions.
>
> This patch fixes a user-land dereference. Now we use
> the safe copy_from_user to access the memory.
>
> Signed-off-by: Scotty Bauer <sbauer@eng.utah.edu>
> ---
> drivers/md/dm-ioctl.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> index 80a4395..39a9d1a 100644
> --- a/drivers/md/dm-ioctl.c
> +++ b/drivers/md/dm-ioctl.c
> @@ -1642,9 +1642,13 @@ static ioctl_fn lookup_ioctl(unsigned int cmd, int *ioctl_flags)
> static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
> {
> uint32_t version[3];
> + uint32_t __user *version_ptr;
> int r = 0;
>
> - if (copy_from_user(version, user->version, sizeof(version)))
> + if (copy_from_user(&version_ptr, &user->version, sizeof(version_ptr)))
> + return -EFAULT;
> +
> + if (copy_from_user(version, version_ptr, sizeof(version)))
> return -EFAULT;
>
> if ((DM_VERSION_MAJOR != version[0]) ||
> @@ -1663,7 +1667,7 @@ static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
> version[0] = DM_VERSION_MAJOR;
> version[1] = DM_VERSION_MINOR;
> version[2] = DM_VERSION_PATCHLEVEL;
> - if (copy_to_user(user->version, version, sizeof(version)))
> + if (copy_to_user(version_ptr, version, sizeof(version)))
> return -EFAULT;
>
> return r;
> --
Friendly ping, is anyone interested in this?
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: dm ioctl: Access user-land memory through safe functions.
2015-12-08 18:26 ` Scotty Bauer
@ 2016-01-05 20:16 ` Mike Snitzer
2016-01-05 21:13 ` Mike Snitzer
0 siblings, 1 reply; 7+ messages in thread
From: Mike Snitzer @ 2016-01-05 20:16 UTC (permalink / raw)
To: Scotty Bauer; +Cc: agk, dm-devel, linux-kernel
On Tue, Dec 08 2015 at 1:26pm -0500,
Scotty Bauer <sbauer@eng.utah.edu> wrote:
>
> On 12/01/2015 11:11 AM, Scotty wrote:
> >
> > 0001-dm-ioctl-Access-user-land-memory-through-safe-functi.patch
> >
> >
> > From b26adf880eba03ac6f2b1dd87426bb96fd2a0282 Mon Sep 17 00:00:00 2001
> > From: Scotty Bauer <sbauer@eng.utah.edu>
> > Date: Tue, 1 Dec 2015 10:52:46 -0700
> > Subject: [PATCH] dm ioctl: Access user-land memory through safe functions.
> >
> > This patch fixes a user-land dereference. Now we use
> > the safe copy_from_user to access the memory.
> >
> > Signed-off-by: Scotty Bauer <sbauer@eng.utah.edu>
> > ---
> > drivers/md/dm-ioctl.c | 8 ++++++--
> > 1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> > index 80a4395..39a9d1a 100644
> > --- a/drivers/md/dm-ioctl.c
> > +++ b/drivers/md/dm-ioctl.c
> > @@ -1642,9 +1642,13 @@ static ioctl_fn lookup_ioctl(unsigned int cmd, int *ioctl_flags)
> > static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
> > {
> > uint32_t version[3];
> > + uint32_t __user *version_ptr;
> > int r = 0;
> >
> > - if (copy_from_user(version, user->version, sizeof(version)))
> > + if (copy_from_user(&version_ptr, &user->version, sizeof(version_ptr)))
> > + return -EFAULT;
> > +
> > + if (copy_from_user(version, version_ptr, sizeof(version)))
> > return -EFAULT;
> >
> > if ((DM_VERSION_MAJOR != version[0]) ||
> > @@ -1663,7 +1667,7 @@ static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
> > version[0] = DM_VERSION_MAJOR;
> > version[1] = DM_VERSION_MINOR;
> > version[2] = DM_VERSION_PATCHLEVEL;
> > - if (copy_to_user(user->version, version, sizeof(version)))
> > + if (copy_to_user(version_ptr, version, sizeof(version)))
> > return -EFAULT;
> >
> > return r;
> > --
>
>
> Friendly ping, is anyone interested in this?
The passed @user argument is flagged via __user so it can be
deferenced directly. It does look like directly deferencing
user->version is wrong.
But even if such indirect access is needed (because __user flag is only
applicable to @user arg, not the contained version member) we could more
easily just do something like this no?:
uint32_t __user *versionp = (uint32_t __user *)user->version;
...
if (copy_from_user(version, versionp, sizeof(version)))
return -EFAULT;
I've staged the following, thanks:
https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.5&id=bffc9e237a0c3176712bcd93fc6a184a61e0df26
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: dm ioctl: Access user-land memory through safe functions.
2016-01-05 20:16 ` Mike Snitzer
@ 2016-01-05 21:13 ` Mike Snitzer
2016-01-07 1:22 ` Scotty Bauer
0 siblings, 1 reply; 7+ messages in thread
From: Mike Snitzer @ 2016-01-05 21:13 UTC (permalink / raw)
To: Scotty Bauer; +Cc: dm-devel, linux-kernel, agk
On Tue, Jan 05 2016 at 3:16pm -0500,
Mike Snitzer <snitzer@redhat.com> wrote:
> On Tue, Dec 08 2015 at 1:26pm -0500,
> Scotty Bauer <sbauer@eng.utah.edu> wrote:
>
> > Friendly ping, is anyone interested in this?
>
> The passed @user argument is flagged via __user so it can be
> deferenced directly. It does look like directly deferencing
> user->version is wrong.
>
> But even if such indirect access is needed (because __user flag is only
> applicable to @user arg, not the contained version member) we could more
> easily just do something like this no?:
>
> uint32_t __user *versionp = (uint32_t __user *)user->version;
> ...
> if (copy_from_user(version, versionp, sizeof(version)))
> return -EFAULT;
>
> I've staged the following, thanks:
> https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.5&id=bffc9e237a0c3176712bcd93fc6a184a61e0df26
Alasdair helped me understand that we do need your original fix.
I've staged it for 4.5 (and stable@) here:
https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.5&id=ead3db62bf10fe143bec99e7b7ff370d7a6d23ef
Thanks again,
Mike
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: dm ioctl: Access user-land memory through safe functions.
2016-01-05 21:13 ` Mike Snitzer
@ 2016-01-07 1:22 ` Scotty Bauer
0 siblings, 0 replies; 7+ messages in thread
From: Scotty Bauer @ 2016-01-07 1:22 UTC (permalink / raw)
To: Mike Snitzer; +Cc: dm-devel, linux-kernel, agk, jmoyer
[-- Attachment #1: Type: text/plain, Size: 2970 bytes --]
On 01/05/2016 02:13 PM, Mike Snitzer wrote:
> On Tue, Jan 05 2016 at 3:16pm -0500,
> Mike Snitzer <snitzer@redhat.com> wrote:
>
>> On Tue, Dec 08 2015 at 1:26pm -0500,
>> Scotty Bauer <sbauer@eng.utah.edu> wrote:
>>
>>> Friendly ping, is anyone interested in this?
>>
>> The passed @user argument is flagged via __user so it can be
>> deferenced directly. It does look like directly deferencing
>> user->version is wrong.
>>
>> But even if such indirect access is needed (because __user flag is only
>> applicable to @user arg, not the contained version member) we could more
>> easily just do something like this no?:
>>
>> uint32_t __user *versionp = (uint32_t __user *)user->version;
>> ...
>> if (copy_from_user(version, versionp, sizeof(version)))
>> return -EFAULT;
>>
>> I've staged the following, thanks:
>> https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.5&id=bffc9e237a0c3176712bcd93fc6a184a61e0df26
>
> Alasdair helped me understand that we do need your original fix.
> I've staged it for 4.5 (and stable@) here:
> https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.5&id=ead3db62bf10fe143bec99e7b7ff370d7a6d23ef
>
> Thanks again,
> Mike
> --
This broke linux-next because I'm dumb and didn't test it. I thought it was a trivial enough of a patch that I wouldn't screw it up, but I did.
I incorrectly assumed that user->version was essentially a pointer in userland, not a flat chunk of memory. Ie it was a pointer to some malloc'd region, not an inlined version[3].
I thought it was this:
struct dm_ioctl {
uint32_t *version;
...
}
It is really this:
struct dm_ioctl {
uint32_t version[3];
}
I was trying to get the values out of *version, which would have been a pointer, but instead what the code ended up doing was actually getting 8 bytes of the version (think 4,3,1) out and trying to access that version as a memory address, oops.
It turns out that the original code is correct and doesn't actually touch user memory without a copy_from_user(). Gcc is smart enough to see that version[3] is inlined, and it can emit code which simply takes the userland pointer (struct dm_ioctl __user user), and calculates on offset based on the pointer, thus no actual user dereference occurs. Had the struct looked like the first example I believe the patch would work.
I'm wondering now if we should switch the code a bit to make it less ambiguous, so someone like me doesn't come along again thinking the code dereferences userland memory and waste everyones time.
I've attached a patch based off linux-next-20150616 which reverts my broken code but adds an & to the front of user->version so it looks like the code is doing the right thing.
If I should be basing my patch off something other than linux-next let me know and I'll rewrite it, or we can just revert the old patch and ignore this one.
Thanks and very sorry for the confusion and breakage.
[-- Attachment #2: 0001-dm-ioctl-disambiguate-the-user-pointer-calculation.patch --]
[-- Type: text/x-patch, Size: 1487 bytes --]
>From 7dde54b74e4543b6f03ceb57f9479a1d402a3fd1 Mon Sep 17 00:00:00 2001
From: Scotty Bauer <sbauer@eng.utah.edu>
Date: Wed, 6 Jan 2016 18:17:35 -0700
Subject: [PATCH] dm ioctl: disambiguate the user pointer calculation
This patch adds an & in front of user->version, in hopes of making
it clear that user-memory is not being touched.
Signed-off-by: Scotty Bauer <sbauer@eng.utah.edu>
---
drivers/md/dm-ioctl.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index fa5bf54..81190df 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1642,13 +1642,9 @@ static ioctl_fn lookup_ioctl(unsigned int cmd, int *ioctl_flags)
static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
{
uint32_t version[3];
- uint32_t __user *versionp;
int r = 0;
- if (copy_from_user(&versionp, &user->version, sizeof(versionp)))
- return -EFAULT;
-
- if (copy_from_user(version, versionp, sizeof(version)))
+ if (copy_from_user(version, &user->version, sizeof(version)))
return -EFAULT;
if ((DM_VERSION_MAJOR != version[0]) ||
@@ -1667,7 +1663,7 @@ static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
version[0] = DM_VERSION_MAJOR;
version[1] = DM_VERSION_MINOR;
version[2] = DM_VERSION_PATCHLEVEL;
- if (copy_to_user(versionp, version, sizeof(version)))
+ if (copy_to_user(&user->version, version, sizeof(version)))
return -EFAULT;
return r;
--
1.9.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: dm ioctl: Access user-land memory through safe functions.
@ 2016-01-07 1:22 ` Scotty Bauer
0 siblings, 0 replies; 7+ messages in thread
From: Scotty Bauer @ 2016-01-07 1:22 UTC (permalink / raw)
To: Mike Snitzer; +Cc: dm-devel, linux-kernel, agk, jmoyer
[-- Attachment #1: Type: text/plain, Size: 2970 bytes --]
On 01/05/2016 02:13 PM, Mike Snitzer wrote:
> On Tue, Jan 05 2016 at 3:16pm -0500,
> Mike Snitzer <snitzer@redhat.com> wrote:
>
>> On Tue, Dec 08 2015 at 1:26pm -0500,
>> Scotty Bauer <sbauer@eng.utah.edu> wrote:
>>
>>> Friendly ping, is anyone interested in this?
>>
>> The passed @user argument is flagged via __user so it can be
>> deferenced directly. It does look like directly deferencing
>> user->version is wrong.
>>
>> But even if such indirect access is needed (because __user flag is only
>> applicable to @user arg, not the contained version member) we could more
>> easily just do something like this no?:
>>
>> uint32_t __user *versionp = (uint32_t __user *)user->version;
>> ...
>> if (copy_from_user(version, versionp, sizeof(version)))
>> return -EFAULT;
>>
>> I've staged the following, thanks:
>> https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.5&id=bffc9e237a0c3176712bcd93fc6a184a61e0df26
>
> Alasdair helped me understand that we do need your original fix.
> I've staged it for 4.5 (and stable@) here:
> https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.5&id=ead3db62bf10fe143bec99e7b7ff370d7a6d23ef
>
> Thanks again,
> Mike
> --
This broke linux-next because I'm dumb and didn't test it. I thought it was a trivial enough of a patch that I wouldn't screw it up, but I did.
I incorrectly assumed that user->version was essentially a pointer in userland, not a flat chunk of memory. Ie it was a pointer to some malloc'd region, not an inlined version[3].
I thought it was this:
struct dm_ioctl {
uint32_t *version;
...
}
It is really this:
struct dm_ioctl {
uint32_t version[3];
}
I was trying to get the values out of *version, which would have been a pointer, but instead what the code ended up doing was actually getting 8 bytes of the version (think 4,3,1) out and trying to access that version as a memory address, oops.
It turns out that the original code is correct and doesn't actually touch user memory without a copy_from_user(). Gcc is smart enough to see that version[3] is inlined, and it can emit code which simply takes the userland pointer (struct dm_ioctl __user user), and calculates on offset based on the pointer, thus no actual user dereference occurs. Had the struct looked like the first example I believe the patch would work.
I'm wondering now if we should switch the code a bit to make it less ambiguous, so someone like me doesn't come along again thinking the code dereferences userland memory and waste everyones time.
I've attached a patch based off linux-next-20150616 which reverts my broken code but adds an & to the front of user->version so it looks like the code is doing the right thing.
If I should be basing my patch off something other than linux-next let me know and I'll rewrite it, or we can just revert the old patch and ignore this one.
Thanks and very sorry for the confusion and breakage.
[-- Attachment #2: 0001-dm-ioctl-disambiguate-the-user-pointer-calculation.patch --]
[-- Type: text/x-patch, Size: 1486 bytes --]
From 7dde54b74e4543b6f03ceb57f9479a1d402a3fd1 Mon Sep 17 00:00:00 2001
From: Scotty Bauer <sbauer@eng.utah.edu>
Date: Wed, 6 Jan 2016 18:17:35 -0700
Subject: [PATCH] dm ioctl: disambiguate the user pointer calculation
This patch adds an & in front of user->version, in hopes of making
it clear that user-memory is not being touched.
Signed-off-by: Scotty Bauer <sbauer@eng.utah.edu>
---
drivers/md/dm-ioctl.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index fa5bf54..81190df 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1642,13 +1642,9 @@ static ioctl_fn lookup_ioctl(unsigned int cmd, int *ioctl_flags)
static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
{
uint32_t version[3];
- uint32_t __user *versionp;
int r = 0;
- if (copy_from_user(&versionp, &user->version, sizeof(versionp)))
- return -EFAULT;
-
- if (copy_from_user(version, versionp, sizeof(version)))
+ if (copy_from_user(version, &user->version, sizeof(version)))
return -EFAULT;
if ((DM_VERSION_MAJOR != version[0]) ||
@@ -1667,7 +1663,7 @@ static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
version[0] = DM_VERSION_MAJOR;
version[1] = DM_VERSION_MINOR;
version[2] = DM_VERSION_PATCHLEVEL;
- if (copy_to_user(versionp, version, sizeof(version)))
+ if (copy_to_user(&user->version, version, sizeof(version)))
return -EFAULT;
return r;
--
1.9.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: dm ioctl: Access user-land memory through safe functions.
2016-01-07 1:22 ` Scotty Bauer
(?)
@ 2016-01-07 2:07 ` Mike Snitzer
-1 siblings, 0 replies; 7+ messages in thread
From: Mike Snitzer @ 2016-01-07 2:07 UTC (permalink / raw)
To: Scotty Bauer; +Cc: dm-devel, linux-kernel, agk, jmoyer
On Wed, Jan 06 2016 at 8:22pm -0500,
Scotty Bauer <sbauer@eng.utah.edu> wrote:
>
>
> On 01/05/2016 02:13 PM, Mike Snitzer wrote:
> > On Tue, Jan 05 2016 at 3:16pm -0500,
> > Mike Snitzer <snitzer@redhat.com> wrote:
> >
> >> On Tue, Dec 08 2015 at 1:26pm -0500,
> >> Scotty Bauer <sbauer@eng.utah.edu> wrote:
> >>
> >>> Friendly ping, is anyone interested in this?
> >>
> >> The passed @user argument is flagged via __user so it can be
> >> deferenced directly. It does look like directly deferencing
> >> user->version is wrong.
> >>
> >> But even if such indirect access is needed (because __user flag is only
> >> applicable to @user arg, not the contained version member) we could more
> >> easily just do something like this no?:
> >>
> >> uint32_t __user *versionp = (uint32_t __user *)user->version;
> >> ...
> >> if (copy_from_user(version, versionp, sizeof(version)))
> >> return -EFAULT;
> >>
> >> I've staged the following, thanks:
> >> https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.5&id=bffc9e237a0c3176712bcd93fc6a184a61e0df26
> >
> > Alasdair helped me understand that we do need your original fix.
> > I've staged it for 4.5 (and stable@) here:
> > https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.5&id=ead3db62bf10fe143bec99e7b7ff370d7a6d23ef
> >
> > Thanks again,
> > Mike
> > --
>
> This broke linux-next because I'm dumb and didn't test it. I thought it was a trivial enough of a patch that I wouldn't screw it up, but I did.
>
> I incorrectly assumed that user->version was essentially a pointer in userland, not a flat chunk of memory. Ie it was a pointer to some malloc'd region, not an inlined version[3].
>
> I thought it was this:
> struct dm_ioctl {
>
> uint32_t *version;
> ...
> }
>
> It is really this:
>
> struct dm_ioctl {
>
> uint32_t version[3];
>
> }
>
> I was trying to get the values out of *version, which would have been a pointer, but instead what the code ended up doing was actually getting 8 bytes of the version (think 4,3,1) out and trying to access that version as a memory address, oops.
>
> It turns out that the original code is correct and doesn't actually touch user memory without a copy_from_user(). Gcc is smart enough to see that version[3] is inlined, and it can emit code which simply takes the userland pointer (struct dm_ioctl __user user), and calculates on offset based on the pointer, thus no actual user dereference occurs. Had the struct looked like the first example I believe the patch would work.
>
> I'm wondering now if we should switch the code a bit to make it less ambiguous, so someone like me doesn't come along again thinking the code dereferences userland memory and waste everyones time.
>
> I've attached a patch based off linux-next-20150616 which reverts my broken code but adds an & to the front of user->version so it looks like the code is doing the right thing.
>
> If I should be basing my patch off something other than linux-next let me know and I'll rewrite it, or we can just revert the old patch and ignore this one.
>
> Thanks and very sorry for the confusion and breakage.
You're fine, no worries.
But I've just dropped the offending original commit from linux-next and
it obviously won't be included in 4.5
I'll revisit whether we need to bother with the extra & change you're
suggesting while coming to terms with why I was able to be lulled into
thinking your original patch was correct ;)
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2016-01-07 2:07 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-12-01 18:11 [PATCH] dm ioctl: Access user-land memory through safe functions Scotty
2015-12-08 18:26 ` Scotty Bauer
2016-01-05 20:16 ` Mike Snitzer
2016-01-05 21:13 ` Mike Snitzer
2016-01-07 1:22 ` Scotty Bauer
2016-01-07 1:22 ` Scotty Bauer
2016-01-07 2:07 ` Mike Snitzer
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.